A base station system is a radio signal transceiver that provides services for mobile users. The base station system includes a Baseband Unit (BBU) and a Radio Remote Unit (RRU), where the BBU and the RRU are connected by using an optical fiber, which may achieve distributed networking.
Existing RRUs have two types of structures. A first type of RRU includes a radio frequency unit, an antenna, and a radio frequency cable. The radio frequency unit includes a Common Public Radio Interface (CPRI), a Digital Analog Converter (DAC)/Analog Digital Converter (ADC), an up- and down-frequency conversion circuit, a Power Amplifier (PA), a Low Noise Amplifier (LNA), and a duplexer. The antenna includes multiple antenna oscillators, where the antenna oscillators are arranged according to a certain rule to implement spatial signal coupling. The radio frequency cable is used to connect the radio frequency unit to the antenna. Specifically, the antenna transmits a received third analog signal to the duplexer in the radio frequency unit through the radio frequency cable; the third analog signal output by the duplexer goes through the LNA, the down-frequency conversion circuit, and the ADC, and then is output to the CPRI; and the CPRI outputs the third analog signal to the BBU. Alternatively, the CPRI outputs a first analog signal received from the BBU to the duplexer through the DAC, the up-frequency conversion circuit, and the PA; the duplexer transmits the first analog signal to the antenna through the radio frequency cable; and the antenna transmits the first analog signal, and samples and trains part of the first analog signal output by the PA to perform Digital Pre-Distortion (DPD) processing. A second type of RRU includes a radio frequency unit. Multiple radio frequency units are arranged according to distances between interior antenna oscillators of an antenna to form an array, so as to satisfy gain and radiation pattern requirements of a base station antenna. The radio frequency unit includes a single antenna oscillator, a DAC/ADC, an up- and down-frequency conversion circuit, a PA, an LNA, and a duplexer. Specifically, the single antenna oscillator outputs a third analog signal to the ADC through the duplexer, the LNA, and the down-frequency conversion circuit; a high-speed digital signal output by the ADC goes through a backplane and is transmitted to a digital board for processing, and then is transmitted to the BBU. Alternatively, the digital board transmits a first analog signal received from the BBU to the DAC through the backplane; the first analog signal output by the DAC is output to the duplexer through the up-frequency conversion circuit and the PA, and then is transmitted by the duplexer to the single antenna oscillator; and the single antenna oscillator transmits the first analog signal, and samples and trains part of the first analog signal output by the PA to perform DPD processing.
In the first type of RRU structure, heat is generated when the first analog signal and the third analog signal go through the radio frequency cable, resulting in loss of the radio frequency cable, which affects efficiency of the base station system to transmit the first analog signal and to receive the third analog signal. In the second type of RRU structure, the backplane transmits the high-speed digital signal, which consumes much power, has high requirements on the backplane, and is expensive, resulting in difficult implementation manner of the base station system.